Xml schema element with attribute and optional simple content?

[Gazza]

I want to define an element type which has child elements which will
have an attribute, but I want the presence of content for these child
elements (which will be simple when present) to be optional. My type is
defined as such

<xsd:complexType name="DistanceStructure">
<xsd:sequence>
<xsd:element name="Value">
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base="xsd:decimal">
<xsd:attribute name="Comment" type="xsd:string"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>
<xsd:element name="Unit">
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base="esdalcommistanceUnitType">
<xsd:attribute name="Comment" type="xsd:string"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
This definition allows validation of the following when it appears in
my instance document


<StructureLength>
<Value Comment="STRUCTURE LENGTH COMMENT">1.1</Value>
<Unit Comment="STRUCTURE LENGTH COMMENT">metre</Unit>
</StructureLength>

But the following does not validate

<StructureLength>
<Value Comment="STRUCTURE LENGTH COMMENT"/>
<Unit Comment="STRUCTURE LENGTH COMMENT"/>
</StructureLength>



I need both to be valid possiblilies in my instance document. What can
I do?

 

[Henry S. Thompson]

<xsd:element name="Value">
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base="xsd:decimal">
<xsd:attribute name="Comment" type="xsd:string"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>

<Value Comment="STRUCTURE LENGTH COMMENT">1.1</Value>

<Value Comment="STRUCTURE LENGTH COMMENT"/>

The empty string is not a valid xs:decimal, so you should define a union
of the empty string (xs:string restricted to length 0, or xs:string
restricted to an enumeration of only "") and xs:decimal, and use that
instead of xs:decimal itself.

ht
--
Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
Half-time member of W3C Team
2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
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URL: http://www.ltg.ed.ac.uk/~ht/
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